<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <meta>
    <title>Document</title>
    <style>
        .flex {
        display: flex;
        width: 200px;
        height: 100px;
    }
    .left {
        flex: 3 2 50px;
        background: red;
    }
    .right {
        flex: 2 1 20px;
        background: blue;
    }
    </style>
    
</head>
<body>
    <div class="flex">
        <div class="left"></div>
        <div class="right"></div>
    </div>
</body>
</html>